1. Field of the Invention
The present invention relates to a pressure tank and a detection method of a pressure tank internal abnormality.
Priority is claimed on Japanese Patent Application No. 2008-176252, filed Jul. 4, 2008, the content of which is incorporated herein by reference.
2. Description of Related Art
In the recent years, a certain kind of pressure tanks for charging gas at a high pressure have been used in some instances, the pressure tank including a kind of container so-called a liner (tank wall) made with aluminum or resin, and the liner being reinforced at the outer surface with Fiber Reinforced Plastic (FRP). FRP is a composite material including plastic and glass or carbon fibers. This kind of pressure tanks possesses advantages of their light weight and high durability against pressure at the same time.
On the other hand, in the application of the aforementioned pressure tanks, there is a concern in that when the tank suffered a damage from some external force, the FRP may be damaged or detached from the liner outer surface, causing an abrupt decrease of the FRP durability. As a result, a concern emerges that the liner reinforced by the liner also cracks.
When the liner cracks, the stress on the liner would be concentrated at the cracked part, resulting in a deformation and progression of the crack. As a result, the pressure-durability of the liner decreases, and the gas charged in the liner may leak. As mentioned above, since the liner is covered by the FRP, the crack in the liner can not be found by visual examination. Therefore, such crack may not be found until the gas actually leaks.
In view of the aforementioned circumstances, as a detection method of pressure tank crack which does not depend on a visual examination, the following constitutions are known.
For example, in the constitution disclosed in the Japanese Unexamined Patent Application, First Publication H2-102450, a supersonic wave probe emits a supersonic wave from the outside of the container, and performs a scan. Thus obtained defects signals based on the reflected echo and the position signal from the position detector are used to compose a section image along the scanning line, or a defect image along the scanning plane.
As another example, the constitution disclosed in Japanese Unexamined Patent Application, First Publication H10-30797, includes a FRP reinforce layer provided at the outside of a liner. The reinforce layer includes a detection circuit having a signal wire. When this signal wire is broken by a damage caused on the FRP reinforce layer, the change in the signal transfer in the detection circuit is used to detect whether the reinforce layer is in a sound condition.
In the recent years, there are cases where the aforementioned pressure tanks are equipped on fuel cell vehicles as a fuel tank. In this case, when the pressure tank is damaged by an accident or the like, the liner may crack, and the gas in the liner may leak.
However, in the constitution of the Japanese Unexamined Patent Application, First Publication H2-102450, since the supersonic wave probe performs a scan while the reflected echo is detected at the same time, it had been impossible to detect abnormalities during a continuous use of the vehicle.
Accordingly, in order to detect cracks on the pressure tank, the pressure tank needs to be unloaded from the vehicle, resulting in high man-hours and costs, and there was a problem in that the overall process was inefficient.
In the constitution of the Japanese Unexamined Patent Application, First Publication H10-30797, the detection circuit included in the reinforce layer is used to detect the abnormality of the reinforce layer. Accordingly, cracks deep inside of the liner, which is provided inside of the reinforce layer, could not be detected. Furthermore, in order to detect smaller cracks, it had been necessary to provide the signal wires at a high density, resulting in an increase in the cost. Although it had been possible to detect cracks by the break of the signal wire, in cases where the signal wire does not break, e.g., when an abnormality happened in the reinforce layer while the reinforce layer was detached from the liner, the abnormality could not be detected.
The present invention was made in view of the aforementioned circumstances: an object of the present invention is to provide a pressure tank in which an internal abnormality can be detected, and to provide a method of pressure tank internal abnormality detection, in which the detection can be performed during a continuous use of the vehicle, while the man-hors and costs are reduced, and the maintenance efficiencies are improved, and while the internal abnormality such as cracks can be reliably and quickly detected.